A kinetic equation is set up for a system of particles interacting with nonadditive intermolecular forces. Bogolyubov's functional assumption is used. After linearizing in the gradients, the kinetic equation is solved by a Chapman-Enskog method. Using the expressions for the stress tensor and heat current obtained in an earlier paper, the contributions of nonadditive forces to the shear and bulk viscosities and thermal conductivity are explicitly obtained. The results obtained are independent of density expansions.

A new derivation is given for the resonance absorption line shape in monatomic gases in terms of resolvent-operator matrix elements. This derivation is believed to be simpler and more rigorous than the one given previously by Reck, Takebe, and Mead. In contrast to the earlier result, in which only diagonal resolvent matrix elements appeared in the expression for the susceptibility, it is shown that off-diagonal elements also contribute. In the classical path approximation, with neglect of excitation transfer via virtual transverse photons, it is shown that the line shapes for emission and absorption are identical. The effect of the off-diagonal elements on the line shape is calculated for the static (statistical) limit, and it is shown to lead to a shift toward the blue. It was previously shown that the off-diagonal terms cause a red shift in the opposite "impact" limit.

Bounds are found for the values of an observable which are consistent with the measured value of a second observable and satisfy the conditions that $f_0\mathrm{}\left(e\right)\mathrm{}$, $f_1\mathrm{}\left(e\right)\mathrm{}$, and $Y\left(e\right)=\frac{f_0^{\prime }\mathrm{}\left(e\right)\mathrm{}}{f_1^{\prime }\mathrm{}\left(e\right)\mathrm{}}$ are well behaved and have nonzero slope on the open interval $e_L \mathrm{to} e_U$. $f_0\mathrm{}\left(e\right)\mathrm{}$ and $f_1\mathrm{}\left(e\right)\mathrm{}$ are, respectively, the contributions to the undetermined and determined observable from an elementary excitation state of energy $e$.

Experimental measurements of the osmotic pressure in liquid ${\mathrm{He}}^3$-${\mathrm{He}}^4$ mixtures made by Landau et al. suggest the possibility of a higher supermobile transition temperature than previously estimated, the possibility of $p$-state pair formation in the supermobile condensate, and the possibility of the existence of zero sound, for mixtures under sufficiently high external pressure.

Phenomena of pressure broadening are discussed using an analogy between the theory of foreign-gas broadening and that of self-broadening. The results are compared with experimental data, and good agreement is obtained.

Previously developed results on the statistical error due to finite time averaging in computer experiments are applied to the number density and kinetic-energy density autocorrelation functions for liquid sodium. It is concluded that the theoretical estimate given by Zwanzig and Ailawadi forms a good basis for analysis of the error involved in computation of time correlation functions in molecular dynamics.

The two-level atom driven near resonance by a very strong classical field is analyzed, and corrections up to second order in the reciprocal field frequency are found to the usual resonant equations of motion. The results are compared to those found recently by Chang and Stehle in a quantum-mechanical formulation of the same problem.

The contributions of double ionization to radiative rates, Auger rates, and fluorescence yields for the filling of atomic $K$-shell vacancies are calculated by use of the classical Gryzinski methods. The double-ionization correction to the ratio of ionization cross sections for $\alpha$ particles and deuterons incident on ${}_{22}{}^{}{}_{}{}^{}\mathrm{Ti}$ is ∼6%. Recent experimental ${}_{22}{}^{}{}_{}{}^{}\mathrm{Ti}$ results of Lewis, Natowiz, and Watson differ from the Born prediction by as much as 7% between 10 and 80 MeV with errors of 2% or less.

An experimental arrangement for the measurement of singly stimulated two-photon emission and anti-Stokes Raman scattering from metastable deuterium atoms is described. The atoms, produced by charge exchange between cesium vapor and 5-keV deuterons, are subjected to intense light pulses from a Nd-glass laser. The generated photons are detected at the exit slit of a vacuum-uv spectrometer. The results are compared with theoretical calculations by Zernik.

The lifetime of the $v=0\mathrm{}$ $c{}_{}{}^3{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ metastable state of ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and HD has been measured using the time-of-flight technique. The velocity distribution of a thermal beam of metastable molecules is sampled and detected at two positions, 1.9 and 6.7 m from the pulsed electron gun used to excite the ground-state molecules effusing from a source slit. A comparison of the number of metastables within specific velocity intervals at the two detectors determines the number which decay in flight and yields an experimental plot of the number which decay versus time of flight. The lifetime $\tau$ is then obtained from the slope ($=-\frac{1}{\tau }$) of a straight line least-squares fitted to the decay plot. The result, $\tau =1.02\mathrm{}\pm 0.05$ msec, is the same for both para-and ortho-${\mathrm{H}}_2$, as well as for ${\mathrm{D}}_2$ and HD. Since all three isotopic combinations have the same measured lifetime, and since the lifetime for a forbidden predissociation through spin-orbit mixing with the ${}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ state would be expected to depend upon details of the fine structure, our value is the radiative lifetime for a combination of magnetic-dipole electric-quadrupole decay of the $v=0\mathrm{}$ $c{}_{}{}^3{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ state to the repulsive ${}_{}{}^3{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ state.

The Landé $g$ factors for some excited levels in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ ii and iii are measured by a beam-foil spectroscopic quantum-beat technique. The values are obtained from ratios of $g$ factors, which are made with a standard $g$ value taken as known. Where comparison is possible, the results of the measurements are generally in agreement with previous Zeeman measurements. In cases where discrepancies are found, the sources of the disagreement are discussed and identified. The technique may be applied to other elements having excited states with lifetimes in the nanosecond range. Other types of $g$-factor measurements for such states are not easily applicable.

Optical hyperfine structure in ${\mathrm{Ne}}^{21}$ has been observed using laser-induced line-narrowing techniques. The output from a long stabilized single-mode 1.15-μ He-Ne laser is focused into an external sample cell containing ${\mathrm{Ne}}^{21}$. The laser field resonates with the ${\mathrm{Ne}}^{21}$ 1.15-μ transition causing changes in the level populations over a narrow velocity range. Viewed along the laser axis, these population changes appear as narrow "change signals" superposed on the Doppler background of the spontaneous emission of the coupled 6096-Å transition. Analysis of the spectrum of these change signals, emitted parallel and antiparallel to the laser-field propagation direction, gives values for the hyperfine $A$ constants for the three levels involved. These constants are analyzed by means of theoretical expressions wherein $〈\frac{1}{r^3}〉$ of the $2p$ hole is the single important parameter. Combining the resulting value of ${〈\frac{1}{r^3}〉}_{2p\mathrm{hole}}$ for the $1s_4$ level with a previous measurement of $B\left(1\mathrm{}{s}_5\right)$ gives a value of $Q\left(1s\right)=(0.093\mathrm{}\pm 0.002)$ b, in agreement with an earlier less-accurate value. In addition, the ${\mathrm{Ne}}^{20,21,22}$ isotope shifts are measured at 1.15 μ and 6096 Å.

Calculated Auger, Coster-Kronig, super Coster-Kronig, and radiative transition rates are used to compute atomic $M$-shell Auger, Coster-Kronig, and fluorescence yields. Comparison is made with five fluorescence-field measurements, with full width at half-maximum measurements of $L-M$ x rays, and with Bhalla's relativistic radiative-yield calculations.

An expression is derived for the Auger transition rate for elements whose initial configuration is described by $j-j$ coupling and whose final configuration is described by Russell-Saunders coupling. We use Asaad's expression for the matrix element when both configurations are described by $j-j$ coupling, and use a transformation from $j-j$ to Russell-Saunders coupling for the two-electron final-state wave function. In addition we obtain expressions for the $M_4\mathrm{NN}$ and $M_5\mathrm{NN}$ transitions which are evaluated in the following paper.

Individual-term electron-transition rates for $M$-shell holes are presented in $j-j$ coupling. As the only available experimental data are best described in the mixed-coupling scheme, further calculations are performed in the mixed-coupling scheme and compared with measured term intensities in Kr and Xe. Agreement is reasonable except for the $(4s, 4p)\left({}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}\right)$ transition in Kr. A tentative identification is made of the $M_{4,5}{N}_1{N}_1$ doublet in Kr and a hypothesis is advanced on the origin of the remaining doublet.

An atomic-beam magnetic-resonance apparatus with separated oscillatory fields has been used to measure the decrease in the ground-state hyperfine energy separation of ${\mathrm{Cs}}^{133}$, ${\mathrm{Rb}}^{87}$, ${\mathrm{Rb}}^{85}$, ${\mathrm{K}}^{39}$, ${\mathrm{Na}}^{23}$, and ${\mathrm{Li}}^7$ because of the presence of a uniform, static, electric field. The hfs frequency shift due to this quadratic Stark effect is designated by $\delta f=-k\times {10}^{-6\mathrm{}}{E}^2$ Hz/${\mathrm{}(\mathrm{V}/\mathrm{c}\mathrm{m})\mathrm{}}^2$. If the ratio $\frac{\delta f\left(X^A\right)}{\delta f\left({\mathrm{Cs}}^{133}\right)}$ is denoted by ${\kappa }_{X^A}$, then the results are ${\kappa }_{{\mathrm{Rb}}^{87}}=0.546\mathrm{}\left(5\right)\mathrm{}$; ${\kappa }_{{\mathrm{Rb}}^{85}}=0.243\mathrm{}\left(1\right)\mathrm{}$, ${\kappa }_{{\mathrm{K}}^{39}}=0.0315\mathrm{}\left(6\right)\mathrm{}$, ${\kappa }_{{\mathrm{Na}}^{23}}=0.0552\mathrm{}\left(12\right)\mathrm{}$, and ${\kappa }_{{\mathrm{Li}}^7}=0.0270\mathrm{}\left(8\right)\mathrm{}$. Existing theories of the alkali-metal Stark effect are discussed, and none is found to give satisfactory agreement with these experimental ratios.

The behavior of electron wave functions near but outside the atomic nucleus is discussed. It is shown that point-Coulomb shapes persist to quite large distances ($r\cong 5{\lambda }_e$, where ${\lambda }_e$ is the Compton electronic wavelength) for bound states and also for energy-shifted continuum states. The screening effects on continuum-state normalizations cancel the screening effects on the kinematic factor $\mathrm{pE}$ in cross sections. These results are used to examine the normalization screening theory in atomic photoeffect, which is characterized by distances both small on an atomic scale and large compared to the size of the nucleus. It is argued that this theory, which describes screening effects simply as a change in normalization, can be good to 1% for photon energies more than 10 keV above the $K$-shell threshold in Al, 30 keV in Cu, 60 keV in Sn, 150 keV in Pb, and 200 keV in U. This agrees well in order of magnitude with exact numerical calculations.